Herbicidal compounds

ABSTRACT

A compound of formula (I):                    
     or a salt, enamine or the like, acylate, sulphonate, carbamate or ether derivative thereof; wherein X, X 1  and X 2  are independently oxygen or sulphur, R 1  is an optionally substituted heterocyclic or cycloalkyl group, and Y is an optionally substituted C 2 -C 4  alkylene group which is optionally interposed by an oxygen atom, a group                    
     a group                    
     or an optionally mono-substituted nitrogen atom, wherein p is 0, 1 or 2, s is 0 or 1 and R b  is alkyl or alkoxy; provided that when X, X 1  and X 2  are oxygen, R 1  is not pyridyl or pyrimidinyl. Processes for the preparation of these compounds and herbicidal compositions containing them are also described and claimed.

This is a continuation of application Ser. No. 09/021,992, filed Feb.11, 1998 now U.S. Pat. No. 5,958,839, which is a continuation ofapplication Ser. No. 08/683,727, filed Jul. 18, 1996, now U.S. Pat. No.5,744,610, which is a continuation of application Ser. No. 08/453,916,filed May 30, 1995, now U.S. Pat. No. 5,563,115, which is a division ofapplication Ser. No. 08/102,004, filed Aug. 4, 1993, now U.S. Pat. No.5,426,091, which is a division of application Ser. No. 07/819,080, filedJan. 10, 1992, now U.S. Pat. No. 5,250,501, which is a division ofapplication Ser. No. 07/595,710, filed Oct. 9, 1990, now U.S. Pat. No.5,098,464, which is a continuation of application Ser. No. 07/170,389,filed Mar. 18, 1988, now abandoned.

The present invention relates to certain herbicidally active substitutedcyclic diones, to processes for their preparation and to compositionscontaining them.

Herbicidal compounds containing a cyclohexane dione coupled to an arylgroup are described and claimed for example in EP-A-90262, EP-A-137,963,EP-A-135,191 and EP-A-186119.

According to the present invention there is provided a compound offormula (I):

or a salt, enamine or the like, acylate, sulphonate, carbamate or etherderivative thereof; wherein X, X¹ and X² are independently oxygen orsulphur; R¹ is an optionally substituted heterocyclic or cycloalkylgroup; and Y is optionally substituted C₂-C₄ alkylene group which isoptionally interposed by an oxygen atom, a group

a group

or an optionally mono-substituted nitrogen atom, wherein p is 0, 1 or 2,s is 0 or 1 and R^(b) is alkyl or alkoxy; provided that when X, X¹ andX² are oxygen, R¹ is not pyridyl or pyrimidinyl.

Compounds of formula (I) can exist in a number of tautomeric forms, forexample:

wherein R¹, X, X¹, X² and Y are as defined in relation to formula (I).Further tautomers exist when Y contains a hydrogen substituent on acarbon atom adjacent to the carbon bearing X¹ or X². It is intended thatall such forms are included within the scope of the invention.

When the compound contains a free hydroxy or thiol group in this way, itmay be derivatised to form salts, in particular agriculturallyacceptable salts, enamines or the like, acylates, sulphonates,carbamates or ethers.

Suitable agriculturally acceptable salts include salts such as sodium,potassium, calcium and ammonium salts.

Examples of ammonium salts include salts with ions of formulaN⁺R^(c)R^(d)R^(e)R^(f) where R^(c), R^(d), R^(e) and R^(f) areindependently selected from hydrogen and C₁₋₁₀ alkyl optionallysubstituted by, for example, hydroxy. Suitably when any of R^(c), R^(d),R^(e) or R^(f) are optionally substituted alkyl, they contain from 1 to4 carbon atoms.

Suitable acylate or ether derivatives are compounds wherein the OHmoiety has been converted to a group of formula —OCOR² or —OR²respectively wherein R² is optionally substituted alkyl having forexample from 1 to 6 carbon atoms, or aryl such as phenyl.

Suitable carbamate derivatives are compounds wherein the OH moiety hasbeen converted to a group

wherein R³ and R⁴ are independently hydrogen or a group R² as definedabove.

Preferably X, X¹ and X² are oxygen.

As used herein the term “enamine or the like” refers to derivativeswhere one of X or X¹ is oxygen and the other is replaced by NR³R⁴, halosuch as fluoro or SR².

These derivatives can be prepared by conventional methods.

Suitable heterocyclic groups R¹ include mono- or fusedbicyclo-heterocyclic rings which may be aromatic or non-aromatic.Suitably R¹ includes up to ten ring atoms up to five preferably three ofwhich may be selected from oxygen, nitrogen and sulphur.

When R¹ is a monocyclic ring, it is suitably a heteroaryl group havingup to 7 ring atoms up to 3 of which are selected from oxygen, nitrogenand sulphur. As used here in the term “heteroaryl” means aromaticheterocyclic.

When R¹ is a fused bicyclic ring, one or both of the rings may containheteroatoms and it may be bonded to the group

by way of either of these rings.

Examples of such heterocyclic groups including furyl, thienyl, pyrrolyl,pyrazolyl, pyridyl, pyrimidinyl, imidazoyl, triazolyl, dithiol,oxathiol, isoxazolyl, oxazolyl, thiazolyl, isothiazolyl, oxadiazolyl,thiodiazolyl, oxatriazolyl, dioxazolyl, oxathiazolyl, oxathiol,dioxinyl, pyridazinyl, pyrazinyl, piperazinyl, priazinyl, oxazinyl,isoxazinyl, oxathiazinyl, morphlinyl, azepinyl, oxepinyl, thiepinyl,diazepinyl, benzofuranyl, isobenzofuranyl, benzothienyl,isobenzothienyl, thionaphthalenyl, isothionaphthalenyl, indolyl,isoindolyl, indazolyl, indoleninyl, isobenzazolyl, pyranopyrrolyl,isoindazolyl, indoxazinyl, benzoxazolyl, benzopyranyl, quinolinyl,isoquinolinyl, cinnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl,naphthyridinyl, pyridopyridinyl, pyranyl, thiopyranyl, chromenyl,thiachromenyl, benzoxazinyl, benzisoxazinyl and purine.

Particular examples of heterocyclic groups R¹ include furyl, thiazolyl,thienyl, benzoxazolyl, pyrazolyl, pyridazinyl, pyrazinyl, benzoxazolyl.

These heterocycles may be linked either through a carbon atom or whenpossible through a nitrogen atom.

Suitable cycloalkyl groups R¹ contain up to 10 ring carbon atoms,preferably up to 7 ring atoms.

Suitable optional substituents for the groups R¹ and R⁸ include one ormore groups selected from oxo, mercapto, halo, such as fluoro, chloro,bromo or iodo, nitro, cyano, amino, mono or dialkylamino, amido, alkyl,alkenyl, alkynyl, cycloalkyl, haloalkyl such as trifluoromethyl,haloalkoxy such as trifluoromethoxy, optionally substituted aryl such asphenyl or naphthyl, hydroxy, alkoxy, alkoxycarbonyl, alkylcarbonyl,mono- or dialkylcarbamoyl, alkylthio, alkylsulphinyl, alkylsulphonyl,sulphonamido, alkylcarbonyloxy, alkylcarbonylamino or heterocyclyl suchas pyridyl and thienyl.

The substituents may be attached to a carbon and/or nitrogen atom of thegroup R¹.

In the above-mentioned list of substituents, the alkyl, alkenyl oralkynyl groups or moieties preferably contain from 1 to 6 carbon atoms.Suitable optional substituents for the aryl groups include halo such asfluoro, chloro or bromo, C₁₋₆ alkyl or C₁₋₆ alkoxy.

In a preferred embodiment, R¹ is a 6-membered heteroaryl ring forexample from one or two nitrogen atoms such as pyridyl, pyrimidinyl,pyridazinyl or pyrazinyl.

In another preferred embodiment, R¹ is a five membered heteroaryl groupor comprises a five-membered heteroaryl group.

For example, R¹ is selected from groups of formula:

wherein R⁵ is hydrogen or C₁-C₄ alkyl, preferably C₁-C₂ alkyl oroptionally substituted aryl such as phenyl;

R⁶, R⁷ and R⁸ independently are (1) hydrogen; (2) halogen, preferablychlorine, fluorine or bromine; (3) C₁-C₄ alkyl, preferably methyl; (4)haloalkoxy, preferably OCF₃; (5) C₁-C₄ alkoxy, preferably methoxy; (6)cyano; (7) nitro; (8) C₁-C₄ haloalkyl, preferably trifluoromethyl; (9)R⁹SOn— wherein n is the integer 0, 1 or 2, preferably 2; and R⁹ is

(a) C₁-C₄ alkyl, preferably methyl;

(b) C₁-C₄ alkyl substituted with halogen, cyano, C₁-C₂ alkoxy or C₁-C₂alkylthio, preferably chloromethyl, difluoromethyl, trifluoromethyl orcyanomethyl;

(c) phenyl; or

(d) benzyl;

(10) —NR¹⁰R¹¹ wherein R¹⁰ and R¹¹ independently are hydrogen or C₁-C₄alkyl; (11) R¹²C(O)— wherein R¹² is C₁-C₄ alkyl or C₁-C₄ alkoxy; (12)—SO₂NR¹⁰R¹¹ wherein R¹⁰ and R¹¹ are as defined above; or (13)—N(R¹⁰)C(O)R¹¹ wherein R¹⁰ and R¹¹ are as defined above.

In particular R¹ is a group of formula:

wherein R⁵ and R⁶ are as defined above.

In particular R⁵ is C₁₋₆ alkyl which may be straight or branched oroptionally substituted phenyl, such as phenyl, p-chlorophenyl,p-methoxyphenyl or p-methylphenyl.

Preferred groups R⁶ are haloalkyl in particular trifluoromethyl.

In a further preferred embodiment R¹ is a bicyclic group of formula

wherein R⁶, R⁷ and R⁸ are as defined above;

One of R¹² or R¹³ is —N═ and the other is C(R¹⁴) wherein R¹⁴ ishydrogen, halogen, such as chlorine, fluorine or bromine; C₁-C₄ alkyl,such as methyl; OCF₃; C₁-C₄ alkoxy, such as methoxy; cyano; nitro; C₁-C₄haloalkyl, such as trifluoromethyl; R¹⁵SOm wherein m is the integer 0, 1or 2, preferably 2; and R¹⁵ is C₁-C₄ alkyl, such as methyl.

In addition R¹ may be a bicyclic group of sub formula

wherein Z is a five or six membered saturated or unsaturated fused ringcontaining up to three heteroatoms selected from oxygen, sulphur andnitrogen. Preferably the ring Z contains two oxygen atoms or an oxygenor sulphur and a nitrogen atom. Thus examples of the group R¹ include

where R⁶ is as defined above.

Suitable optional substituents for the group Y include those listedabove for R¹. In addition substituents on adjacent carbon atom s in thegroup Y may be joined together to form a fused ring system. The fusedring may be aromatic or non-aromatic and may be optionally substitutedby one or more substituents listed above for R¹. For example, the group

may be the group:

Preferably Y is a group of formula:

wherein R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ are independently selected fromhydrogen, C₁₋₄ alkyl, C₁₋₄ alkanoyl or —CO₂R²² wherein R²² is C₁₋₄ alkylor R¹⁶ and R¹⁷ or R¹⁸ and R¹⁹ or R²⁰ and R²¹ together with the carbonatom to which they are attached form a C₃₋₆ cycloalkyl ring; and q is 0or 1. Most preferably q is 1.

Other examples of the group Y are

wherein R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰, R^(b), s and p are as hereinbeforedefined and R²³ is alkyl or alkoxy preferably having up to 6 carbonatoms.

In particular the group

is a group of formula

A suitable alkanoyl group for R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ is acetyl.

Preferably only one of R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ is eitheralkanoyl or —CO₂R².

Preferably R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ are hydrogen or C₁₋₄ alkyl inparticular C₁₋₂ alkyl.

Most preferably R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ hydrogen or methyl.

A particularly preferred sub-group of compounds are compound of formula(IA):

or a salt, acylate or sulphonate derivative thereof; wherein R²⁵ is anoptionally substituted heteroaryl group, R¹⁶, R¹⁷, R²⁰ and R²¹ are ashereinbefore defined, provided that at least R¹⁶ and R¹⁷ or R²⁰ and R²¹are not both hydrogen and that not more than two of R¹⁶, R¹⁷, R²⁰ andR²¹ are C₁₋₄ alkanoyl or —CO₂R²².

Most preferably R¹⁶, R¹⁷, R²⁰ and R²¹ are C₁₋₄ alkyl in particularmethyl.

Examples of compounds of formula (I) are set out in Tables I and II.

TABLE 1

COMPOUND CHARACTERISING NO. R¹ R² R³ R⁴ R⁵ R⁶ R⁷ DATA  1

H H CH₃ CH₃ H H M⁺ 250 δ8.14 (d, 1); 7.70 (d, 1); 7.12 (dd, 1); 2.54(broad s, 4); 1.12 (s, 6); 1760 (broad s, 1).  2

H H H H H H M⁺ 222 δ8.06 (d, 1); 7.68 (d, 1); 7.10 (dd, 1); 2.64 (broads, 4); 2.04 (M, 2); 1730 (broad s, 1).  3

H H CH₃ CH₃ H H MH⁺ 319, (M-Cl)⁺ 283δ 6.80 (s, 1); 2.64 (s, 2); 2.40 (s,2); 1.12 (s, 6); 16.75 (s, 1) all peaks  4

H H H H H H MH⁺ 291, (M-C1)⁺ 255δ 6.80 (s, 1); 2.74 (t, 2); 2.50 (t, s);2.04 (M, 2); 16.94 (s, 1).  5

H H CH₃ CH₃ H H M⁺330 δ8.0 (d, 1); 7.12 (d, 1); 2.54 (broad s, 4); 1.12(s, 6).  6

H H H H H H M⁺236, M⁺-CH₃ 221δ 7.46 (d, 1); 6.87 (d, 1); 2.61 (broad,4), 2.06 (M, 2); 16.6 (broad s, 1).  7

CH₃ CH₃ H H H H H-NMR (CDCl₃); δ1.31 (s, 2 CH₃), 1.91 (s, CH₃), 2.71 (t,CH₂), 7.62 (s, ar.H); MS: 168, 170, 196, 198, 224, 226, 280, (M⁺), 282 8

CH₃ CH₃ H H H H H-NMR (CDCl₃); δ1.06 (s, CH₃), 1.23 (s, CH₃), 1.85 (t,CH₂), 2.61 (t, CH₂), 8.45 (s, ar.H), 8.50 (s, ar.H); MS: 113, 128, 130,141, 143, 168, 170, 196, 198, 209, 211, 224, 226, 265, 267, 280 (M⁺),282  9

H H H H H H H-NMR (CDCl₃); δ2.09 (m, CH₂), 2.67 (br.s, 2CH₂), 7.00 (d,ar.H), 8.06 (d, ar.H), 15.13 (br.s, OH); MS: 145, 147, 200, 202, 221,256 (M⁺), 258 10

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.31, 1.67 (s, 2CH₃), 1.92 (t, CH₂),2.73 (t, CH₂), 7.13 (d, ar.H) 8.1 (d, ar.H); MS: 145, 147, 162, 164,200, 202, 228, 284 (M⁺), 286 11

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.37(s, 2CH₃), 1.88 (t, CH₂), 2.38 (s,CH₃), 2.69 (t, CH₂), 6.92 (d, ar.H), 7.47 (d, ar.H) 7.47 (d, ar.H); MS:125, 138, 167, 249, 264 M⁺) 12

H H H H H H H-NMR (CDCl₃): δ2.01 (m, CH₂). 2.49 (s, CH₃), 2.68 (br.m.2CH₂), 6.81 (d, ar.H), 7.98 (d, ar.H), 17.0 (br.s.OH): MS: 125, 152,180, 236 (M⁺) 13

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.22 (s, 2CH₃), 1.83 (t, CH₂), 2.52 (s,CH₃), 2.68 (t, CH₂), 6.72 (d, ar.H), 7.82 (d, ar.H); MS: 125, 152, 180,193, 208, 264 (M⁺) 14

H H H H H H H-NMR (CDCl₃): δ1.99 (m, CH₂), 2.62 (t, 2CH₂), 8.02 (s,ar.H), 17.33 (br.s, OH); MS: 220, 267, 269, 271, 299, 301, 378 (M⁺),380, 382 15

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.28 (s, 2CH₃), 1.87 (t, CH₂), 2.75(br.t.CH₂) 8.00 (s, ar.H); MS: 139, 267, 269, 271, 322, 324, 326, 327;328, 329, 350, 352, 354, 406 (M⁺), 408, 410 16

H H H H H H H-NMR (CDCl₃ + DMSO-d₆): δ2.08 (m.CH₂), 2.52 (t, 2CH₂), 7.408.01 (m, 4 ar.H); MS: 195, 242, 271 (M⁺ - Cl) 17

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.26 (s, 2CH₃), 1.90 (t, CH₂), 2.72(t,CH₂), 7.41 (m, 2 ar.H), 7.81 (m, 2ar.H); MS: 195, 242, 299 (M⁺- Cl)18

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.27 (s, 2CH₃), 1.88 (t, CH₂), 2.68 (t,CH₂), 6.68 (s, ar.H); MS: 179, 181, 226, 228, 265, 267, 283 (M⁺ - Cl),285, 287 19

H H H H H H H-NMR (CDCl₃): δ2.17 (m, CH₂), 2.68 (br.m, 2CH₂), 7.51 (a,ar.H); MS: 299 (M⁺ - Br), 301 20

H H H H H H H-NMR (CDCl₃): δ2.06 (m, CH₂), 2.62 (br.m, 2CH₂), 7.41 (s,ar.H); MS: 179, 181, 226, 225 (M⁺- Cl), 257, 289 (M⁺ - H), 291 21

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.34 (s, 2CH₃), 2.00 (t, CH₂), 2.80 (t,CH₂), 7.50 (s, ar.H); MS: 179, 181, 199, 201, 265, 267, 283 (M⁺ - Cl),285, 317 (M⁺- H), 319 22

H H H H H H H-NMR (CDCl₃ + DHSO-d₆): δ2.17 (m, CH₂), 263, (t, 2CH₂),7.52 (s, ar.H); MS: 139, 177, 205, 251 (M⁺) 23

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.31 (s, 2CH₃), 1.98 (t, CH₂), 2.76 (t,CH₂), 7.44 (d, ar.H), 7.50 (d, ar.H); MS: 167, 176, 195, 223, 233, 251,279 (M⁺), 280 24

H H H H H H H-NMR (CDCl₃ + DMSO-d₆): δ2.00 (m, CH₂), 2.45 (t, 2CH₂),3.85 (s, CH₃), 6.00 (dd, ar.H), 6.68 (dd, ar.H), 6.95 (dd, ar.H); MS:108, 139, 202, 219 (M⁺) 25

H H CH₃ CH₃ H H H-NMR (CDCl₃): δ1.14 (s, 2CH₃), 2.42 (s, 2CH₂), 3.90 (s,CH₃N), 6.15 (dd, ar.H), 6.86 (m, 2 ar.H); MS: 108, 135, 167, 230, 247(M⁺) 26

H H H H H H H-NMR (CDCl₃): δ2.10 (m, CH₂), 2.58 (br.m, 2CH₂), 3.88 (s,CH₃N), 7.04 (s, ar.H), 7.3- 7.7 (m, 4 ar.H); MS: 130, 131, 139, 144,158, 269 (M⁺) 27

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.30 (s, 2CH₃), 1.90 (t, CH₂), 2.62 (t,CH₂), 3.84 (s, CH₃N), 6.88 (s, ar.H), 7.00-7.6 (m, 4 ar.H); MS: 130,131, 158, 167, 185, 213, 241, 280, 297 (M⁺) 28

H H CH₃ CH₃ H H H-NMR (CDCl₃): δ1.10 (s, 2CH₃), 2.38 (s, 2CH₂), 3.90 (s,CH₃N), 6.90 (s, ar.H), 7.00-7.55 (m,4 ar.H); MS: 130, 131, 158, 167,280, 297 (M⁺) 29

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.23 (s, 2CH₃), 1.91 (t, CH₂), 2.70(t,CH₂), 3.16 (s, CH₃SO₂), 4.03 (s, CH₃N), 6.54 (d, ar.H), 6.85 (d,ar.H); MS: 159, 167, 172, 173, 186, 246, 325 (M⁺) 30

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.08 (s, 2CH₃), 1.80 t, CH₂), 2.53 (m,CH₂), 2.63 (t, CH₃CO), 3.21 (s, CH₃ SO₂), 3.80 (s, CH₃N), 6.95 (s,ar.H); MS: 167, 186, 215, 228, 324, 367 (M⁺) 31

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.16 (s, 2CH₃), 1.97 (t, CH₂), 2.68 (t,CH₂), 7.8-8.15 (m, 4ar.H), 8.97 (s, ar.H); MS: 129, 144, 156, 184, 212,226, 240, 296 (M⁺) 32

H CH₃ CH₃ H H H H-NMR (CDCl₃): δ1.10 (s, 2CH₃), 2.50 (s, 2CH₂),7.81-8.17 (m, 4ar.H), 9.00 (s, ar.H), 13.3 .(br.s.OH); MS: 129, 130,144, 156, 184, 212, 240, 296 (M⁺) 33

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.15 (s, CH₃), 1.27 (s, CH₃), 2.00 (m,CH₂), 2.76 (m, CH₂), 7.7-8.8 (m 6 ar.H); MS: 128, 143, 156, 211, 239,295 (M⁺) 34

H H H H H H MS: 128, 129, 143, 156, 173, 211, 267 (M⁺) 35

H H H H H H mp. 110-130° C. 36

H H H H H H H-NMR (CDCl₃): δ2.2 (m, CH₂), 2.7 (br.m.2CH₂), 8.8.45 (m,3ar.H), 8.95 (s,ar.H); MS: 139, 149, 183, 208, 210, 318, 320, 346 (M⁺),348 37

H H H H H H H-NMR (CDCl₃): δ2.10 (m, CH₂), 2.66 (t, 2CH₂), 13.70 (br.s,OH); MS: 180, 182, 184, 227, 229, 256 (M⁺ - Cl), 258 38

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.32 (s, 2CH₃), 1.98 (t, CH₂), 2.80 (t,CH₂); MS: 180, 182, 184, 227, 229, 255, 257, 284 (M⁺ - Cl), 286 39

H H H H H H H-NMR (CDCl₃): δ2.05 (m, CH₂), 2.58 (t, 2CH₂), 2.63 (s,CH₃S), 2.71 (s, CH₃S); MS: 103, 139, 144, 177, 204, 268 (M⁺ - CH₃S) 40

H H H H H H H-NMR (CDCl₃): δ2.10 (m, CH₂), 2.18 (s, CH₃), 2.61 (m,2CH₂), 3.40 (s, CH₃SO), 3.95 (s, CH₃N); MS: 139, 174, 201, 233, 295,297, 312 (M⁺) 41

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.30 (s, 2CH₃, 1.91 (t, CH₂), 2.19 (s,CH₃), 2.71 (t, CH₂), 3.38 (s, CH₃SO₂), 3.92 (s, CH₃N); MS: 167, 174,187, 201, 325, 340 (M⁺) 42

H H H H H H H-NMR (CDCl₃): δ1.1-2.0 (br.m.2CH₂), 2.5 (br.m.CH₂), 3.9(s,CH₃N), 7.9 (s, ar.H); MS: 177, 219, 232, 269, 288 (M⁺) 43

CH₃ CH₃ H H H H H-NMR (CDCl₃): δ1.13 (br.s. 2CH₃), 1.78 (t, CH₂), 2.6(br.m.CH₂) (3.88 (s, CH₃N), 7.85 (s, ar.H); MS: 177, 232 247, 260, 316(M⁺) 44

H H H H H H mp. 60-64° C. 45

CH₃ CH₃ H H H H glass 46

H H H H H H Semi solid 47

CH₃ CH₃ H H H H Semi solid 48

H H H H H H Dark oil 49

H H H H H H Oil 50

CH₃ CH₃ H H H H Oil 51

H H H H H H mp 128-131° C. 52

CH₃ CH₃ H H H H Glass 53

H H H H H H M pt. 90-100° C. 54

H H H H H H M pt 110-114° C. 55

CH₃ CH₃ H H H H M pt 105-108° C. 56

H H H H H H M pt. 112-115° C. 57

CH₃ CH₃ H H H H M pt 71-76° C. 58

H H H H H H mp. 31-35° C. 59

CH₃ CH₃ H H H H 60

CH₃ CH₃ H H H H mp. 75-82° C. 61

H H H H H H mp. 70-74 62

CH₃ CH₃ H H H H oil 63

H H H H H H mp. 126-128° C. 64

CH₃ CH₃ H H H H mp. 98-100° C. 65

H H H H H H mp. 100-102° C. 66

CH₃ CH₃ H H H H oil 67

H H H H H H mp. 135-145 68

H H H H H H mp. 104-106° C. 69

CH₃ CH₃ H H H H mp. 60-65° C. 70

H H H H H H mp. 94-104° C. 71

CH₃ CH₃ H H H H mp. 89-93° C. 72

H H H H H H ¹H NMR (CDCl₃): δ2.06 (t, CH₂); 2.42 (t CH₂); 2.70 (t, CH₂);4.23 (m, 2CH₂); 6.94 (m, ar, H); 7.06 (tr, s.OH) 73

H H H H H H mp. 80-82° C. 74

H H H H H H mp. 156-7° C. 75

H H H H H H mpt. 139-140° C. 76

H H H H H H mpt. 143-144° C. 77

H H H H H H mpt. 105-106° C.

TABLE II

COMPOUND CHARACTERISING NO. R¹ R² R³ R⁶ R⁷ DATA 78

CH₃ CH₃ CH₃ CH₃ mpt. 103-105° C. 79

CH₃ CH₃ CH₃ CH₃ mpt. 90-93° C. 80

CH₃ CH₃ CH₃ CH₃ Oil ¹H NMR 270 MHz, CDCl₃) δ 1.34 (s,6H); 1.47 (s,6H);2.64 (s,3H); 2.70 (s,3H) 81

CH₃ CH₃ CH₃ CH₃ Oil ir (nujol) 1720, 1670, 1560 cm⁻¹ 82

CH₃ CH₃ CH₃ CH₃ mpt. 90-93° C.

Compounds of formula (I) can be prepared by rearrangement of a compoundof formula (II):

wherein R¹, X, X¹, X² and Y are as defined in relation to formula (I) inthe presence of a cyanide source and a moderate base.

The reaction is suitably carried out in an inert organic solvent such asacetonitrile and at a temperature of from −30° C. to 90° C., preferablyat from 20° C.-40° C.

Suitable cyanide sources are alkali metal cyanides such as sodium andpotassium cyanide; cyanohydrins of methyl alkyl ketones having from 1-4carbon atoms in the alkyl groups, such as acetone or methyl isobutylketone cyanohydrins; cyanohydrins of benzaldehyde or of C₂-C₅ aliphaticaldehydes such as acetaldehyde, propionaldehyde, etc., cyanohydrins;zinc cyanide; tri(lower alkyl)silyl cyanides, notably trimethyl silylcyanide; and hydrogen cyanide itself.

A preferred cyanide source is acetone cyanohydrin.

The amount of the cyanide source employed is sufficient to catalyse thereaction, for example from 1-50 mole percent of the compound of formula(II), preferably from 1 to 10 mole percent.

Moderate bases suitable for use in this reaction include both organicbases such as tertiary amines and inorganic bases such as alkali metalcarbonates and phosphates. Suitable tertiary amines includetrialkylamines such as triethylamine, trialkanolamines such astriethanolamine, and pyridine. Suitable inorganic bases includepotassium carbonate and trisodium phosphate.

Suitably the base is used in an amount of from about 1 to about 4 molesper mole of compound of formula (II), preferably about 2 moles per mole.

Compounds of formula (II) can be prepared by reacting a compound offormula (III):

wherein X¹, X², and Y are as defined in relation to formula (I) with acompound of formula (IV):

R¹CXZ  (IV)

wherein R¹ and X are as defined in relation to formula (I) and Z is aleaving group, in the presence of a base.

Suitable bases for use in the reaction are the moderate bases describedabove for use in the rearrangement of the compound of formula (II). Apreferred base is triethylamine.

Suitable leaving groups Z include halide such as chloride.

The reaction is suitably carried out in an inert organic solvent such asdichloromethane, 1,2-dichloroethane, toluene, acetonitrile, ordimethylformamide at moderate temperatures of from 0° C. to 50° C.,conveniently at room temperature.

Compounds of formula (II) may also be prepared by reacting a compound offormula (III) with an acid of formula (V):

R¹CXOH  (V)

wherein R¹ and X are as defined in relation to formula (I), in thepresence of a dehydrating agent and a basic organic catalyst.

Suitable dehydrating agents include dicyclohexylcarbodiimide (DCC) whichis employed in an amount of at least one molar equivalent to thecompounds of formulae (III) and (V).

Examples of suitable basic organic catalysts include4-dimethylaminopyridine (DMAP) and 4-pyrrolidinopyridine (PPY).

The reaction is suitably carried out in an inert organic solvent such asacetonitrile, tetrahydrofuran, dichloromethane or 1,2-dichloroethane.Moderate temperatures for example from 0° C. to 40° C. can be employed,conveniently ambient temperature.

Alternatively a compound of formula (I) can be prepared by reacting acompound of formula (III) as hereinbefore defined with a compound offormula (VI):

R¹CXCN  (VI)

wherein R¹ and X are as hereinbefore defined, in the presence of a baseand a Lewis acid.

Suitable bases are the moderate bases described above for use in therearrangement of the compound of formula (II).

Suitable Lewis acids are zinc chloride and aluminum trichloride,preferably zinc chloride.

The reaction is carried out in an organic solvent such as acetonitrileor methylene chloride and at moderate temperatures of from −20° C. to+40° C.

Suitably both the zinc chloride and the base are present in a slightmolar excess with respect to the compounds of formula (III) and (VI).

Compounds of formulae (III), (IV), (V) and (VI) are either knowncompounds or they can be prepared from known compounds by conventionalmethods.

For instance a particular example of a compound of formula (V) arecompounds of formula (VA)

wherein R⁵ and R⁶ are as defined above.

These compounds can be prepared as set out in Scheme A.

Suitable conditions for the first stage in Scheme A are found in anarticle, see R Jones JACS, 73 3686.

Conditions from the two subsequent steps are outlined in GB 2,149,402A.

A particular example of a compound of formula (III) is a compound offormula (IIIA):

Compounds of formula (IIIA) wherein R¹⁶, R¹⁷, R²⁰ and R²¹ are methyl orhydrogen and their preparation are described by Riedl and Risse (JustusLiebigs Annalen der Chemie, 1954, 585, 209).

Compounds of formula (IIIA) wherein R¹⁶, R¹⁷, R²⁰ and R²¹ are the sameand are C₁₋₄ alkyl can be prepared by the following reaction Scheme B.

wherein X′ is a leaving group such as halide, in particular iodide.Suitable reaction conditions will be apparent by analogy with theabove-mentioned publication. For example, one suitable base for use inthe first step in Scheme B is sodium methoxide in methanol. A suitableacid for use in second step of Scheme B is an inorganic acid such ashydrochloric acid.

By adjusting the conditions in the first step of the process, it may bepossible to obtain compounds of formula (IIIA) wherein R²⁰ and/or R²¹are hydrogen.

Alternatively compounds of formula (IIIA) can be prepared using themethods described by Murin et al (Chem. Ber. 1959, 92, 2033) or methodsanalogous thereto.

In this way compounds of formula (IIIA) are prepared by cyclisation of acompound of formula (VII):

in the presence of a base such as sodium methoxide an organic solventsuch as methanol. Compounds of formula (VII) can be prepared as outlinedin Scheme C.

Precise reaction conditions for each step in Scheme B will depend uponthe particular compounds involved and can be determined by routineprocedures and the relevant literature.

Compounds of formula (VIII) can be prepared by the reaction of compoundsof formula (IX):

with a compound of formula R²⁰X′ and optionally thereafter with acompound of formula R²¹X′ in the presence of a base such as sodiummethoxide in an organic solvent such as methanol, wherein R²⁰, R²¹ andX′ are as hereinbefore defined.

When R²⁰ and R²¹ are the same, then the reaction can be carried out in asingle step. By controlling the reaction conditions, the extent of thereaction (i.e. whether one or both hydrogen atoms on the methylene arereplaced by R²⁰) can be determined.

Compounds of formula (IX) can be prepared by reaction of a compound offormula (X):

wherein R¹⁶ and R¹⁷ are as hereinbefore defined, with (a) a strong basesuch as lithium diisopropyl-amide and (b) CH₃O₂CCl under conventionalreaction conditions.

Compounds of formula (X) can be prepared by reacting a compound offormula (XI):

with a compound of formula R¹⁶X′ in the presence of a base; andoptionally thereafter R¹⁷X′ wherein R¹⁶, R¹⁷ and X′ are hereinbeforedefined, as described above for the reaction of the compound of formula(IX).

Alternatively compounds of formula (IA) can be prepared by reacting acompound of formula (VIIIA) as set out in Scheme C with a compound offormula (XII):

wherein R¹ is as hereinbefore defined, in the presence of aluminumtrichloride.

Reactions of this type are described by Merenyi and Nilson (Acta Chem.Scand, 1963, 17, 1801 and Acta Chem. Scand, 1964, 18, 1368).

Compounds of formula (XII) are known compounds or they can be preparedfrom known compounds by conventional methods.

Furthermore, compounds of formula (IA) wherein R¹⁶, R¹⁷, R²⁰ and R²¹ arethe same, can also be prepared by reacting a compound of formula (XIII):

with a compound of formula R¹⁶X′ in the presence of a base, wherein R¹,R¹⁶ and X′ are as hereinbefore defined.

Suitable bases for use in the reaction are strong bases such as sodiummethoxide.

The reaction is suitably carried out in an organic solvent such asmethanol at temperatures of from 0 to 100° C.

The compounds of formula (I) are active as herbicides and therefore, ina further aspect the invention provides a process for severely damagingor killing unwanted plants which process comprises applying to theplants, or to the growth medium of the plants, an effective amount of acompound of formula (I) as hereinbefore defined.

The compounds of formula (I) are active against a broad range of weedspecies including monocotyledenous and dicotyledonous species. They mayshow some selectivity towards certain species, in particular maize.

The compounds of formula (I) may be applied directly to the plant(post-emergence application) or to the soil before the emergence of theplant (pre-emergence application).

The compounds of formulae (I) may be used on their own to inhibit thegrowth of, severely damage, or kill plants but are preferably used inthe form of a composition comprising a compound of the invention inadmixture with a carrier comprising a solid or liquid diluent.

Therefore, in yet a further aspect the invention provides plant growthinhibiting, plant damaging, or plant killing compositions comprising acompound of formula (I) as hereinbefore defined and an inert carrier ordiluent.

Compositions containing compounds of formula (I) include both dilutecompositions, which are ready for immediate use, and concentratedcompositions, which require to be diluted before use, usually withwater. Preferably the compositions contain from 0.01% to 90% by weightof the active ingredient. Dilute compositions ready for use preferablycontain from 0.01 to 2% of active ingredient, while concentratedcompositions may contain from 20 to 90% of active ingredient, althoughfrom 20 to 70% is usually preferred.

The solid compositions may be in the form of granules, or dustingpowders wherein the active ingredient is mixed with a finely dividedsolid diluent, eg, kaolin, bentonite, kieselguhr, dolomite, calciumcarbonate, talc, powdered magnesia, Fuller's earth and gypsum. They mayalso be in the form of dispersible powders or grains, comprising awetting agent to facilitate the dispersion of the powder or grains inliquid. Solid compositions in the form of a powder may be applied asfoliar dusts.

Liquid compositions may comprise a solution or dispersion of an activeingredient in water optionally containing a surface-active agent, or maycomprise a solution or dispersion of an active ingredient in awater-immiscible organic solvent which is dispersed as droplets inwater.

Surface-active agents may be of the cationic, anionic, or non-ionictype. The cationic agents are, for example, quaternary ammoniumcompounds (eg cetyltrimethylammonium bromide). Suitable anionic agentsare soaps; salts or aliphatic mono ester of sulphuric acid, for examplesodium lauryl sulphate; and salts of sulphonated aromatic compounds, forexample sodium dodecylbenzenesulphonate, sodium, calcium, and ammoniumlignosulphonate, butylnaphthalene sulphonate, and a mixture of thesodium salts of diisopropyl and triisopropylnaphthalenesulphonic acid.Suitable non-ionic agents are the condensation products of ethyleneoxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, orwith alkylphenols such as octyl- or nonyl-phenol or octyl-cresol. Othernon-ionic agents are the partial esters derived from long chain fattyacids and hexitol anhydrides, for example sorbitan monolaurate; thecondensation products of the partial ester with ethylene oxide; and thelecithins.

The aqueous solutions or dispersions may be prepared by dissolving theactive ingredient in water or an organic solvent optionally containingwetting or dispersing agent(s) and then, when organic solvents are used,adding the mixture so obtained to water optionally containing wetting ordispersing agent(s). Suitable organic solvents include, for example,ethylene di-chloride, isopropyl alcohol, propylene glycol, diacetonealcohol, toluene, kerosene, methylnaphthalene, the xylenes andtrichloroethylene.

The compositions for use in the form of aqueous solutions or dispersionsare generally supplied in the form of a concentrate containing a highproportion of the active ingredient, and the concentrate is then dilutedwith water before use. The concentrates are usually required towithstand storage for prolonged periods and after such storage, to becapable of dilution with water to form aqueous preparations which remainhomogeneous for a sufficient time to enable them to be applied byconventional spray equipment. Concentrates conveniently contain 20-90%,preferably 20-70%, by weight of the active ingredient(s). Dilutepreparations ready for use may contain varying amounts of the activeingredient(s) depending upon the intended purpose; amounts of 0.01% to10.0% and preferably 0.1% to 2%, by weight of active ingredient(s) arenormally used.

A preferred form of concentrated composition comprising the activeingredient which has been finely divided and which has been dispersed inwater in the presence of a surface-active agent and a suspending agent.Suitable suspending agents are hydrophilic colloids and include, forexample, polyvinylpyrrolidone and sodium carboxymethylcellulose, and thevegetable gums, for example gum acacia and gum tragacanth. Preferredsuspending agents are those which impart thixotropic properties too, andincrease the viscosity of the concentrate. Examples of preferredsuspending agents include hydrated colloidal mineral silicates, such asmontmorillonite, beidellite, nontronite, hectorite, saponite, andsaucorite. Bentonite is especially preferred. Other suspending agentsinclude cellulose derivatives and polyvinyl alcohol.

The rate of application of the compounds of the invention will depend ona number of factors including, for example, the compound chosen for use,the identity of the plants whose growth is to be inhibited, theformulations selected for use and whether the compound is to be appliedfor foliage or root uptake. As a general guide, however, an applicationrate of from 0.005 to 20 kilograms per hectare is suitable while from0.1 to 10 kilograms per hectare may be preferred.

The compositions of the invention may comprise, in addition to one ormore compounds of the invention, one or more compounds not of theinvention but which possess biological activity. Accordingly in yet astill further embodiment the invention provides a herbicidal compositioncomprising a mixture of at least one herbicidal compound of formula (I)as hereinbefore defined with at least one other herbicide.

The other herbicide may be any herbicide not having the formula (I). Itwill generally be a herbicide having a complementary action in theparticular application. For example it may be desirable in certaincircumstances to use the compound of formula (I) in admixture with acontact herbicide.

Examples of useful complementary herbicides include:

A. benzo-2,1,3-thiadiazin-4-one-2,2-dioxides such as3-isopropylbenzo-2,1,3-thiadiazin-4-one-2,2-dioxide (bentazon);

B. hormone herbicides, particularly the phenoxy alkanoic acids such as4-chloro-2-methylphenoxy acetic acid (MCPA),2-(2,4-dichlorophenoxy)propionic acid (dichlorprop),2,4,5-trichlorophenoxyacetic acid (2,4,5-T),4-(4-chloro-2-methylphenoxy)butyric acid (MCPB),2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butyricacid (2,4-DB), 2-(4-chloro-2-methylphenoxy)propionic acid (mecoprop),and their derivatives (eg. salts, esters and amides);

C. 3-[4-(4-halophenoxy)phenyl]-1,1-dialkylureas such as3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea.

D. Dinitrophenols and their derivatives (eg. acetates) such as2-methyl-4,6-dinitrophenol (DNOC), 2-t-butyl-4,6-dinitrophenol(dinoterb), 2-secbutyl-4,6-dinitrophenol (dinoseb) and its ester,dinoseb acetate;

E. dinitroaniline herbicides such asN′,N′-diethyl-2,6-dinitro-4-trifluoromethyl-m-phenylenediamine(dinitramine), 2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline(trifluralin) and 4-methylsulphonyl-2,6-dinitro-N,N-dipropylaniline(nitralin);

F. phenylurea herbicides such asN′-(3,4-dichlorophenyl)-N,N-dimethylurea (diuron) andN,N-dimethyl-N′-[3-(trifluoromethyl)phenyl]urea (flumeturon);

G. phenylcarbamoyloxyphenylcarbamates such as 3-[methoxycarbonylamino]phenyl(3-methylphenyl)carbamate (phenmedipham) and3-[ethoxycarbonylamino]phenyl phenylcarbamate (desmedipham);

H. 2-phenylpyridazin-3-ones such as5-amino-4-chloro-2-phenylpyridazin-3-one (pyrazon);

I. uracil herbicides such as 3-cyclohexyl-5,6-tri-methyleneuracil(lenacil), 5-bromo-3-sec-butyl-6-methyl-uracil (bromacil) and3-t-butyl-5-chloro-6-methyl-uracil (terbacil);

J. triazine herbicides such as2-chloro-4-ethylamino-6-(i-propylamino)-1,3,5-triazine (atrazine),2-chloro-4,6-di(ethylamino)-1,3,5-triazine (simazine) and2-azido-4-(i-propylamino)-6-methylthio-1,3,5-triazine (aziprotryne);

K. 1-alkoxy-1-alkyl-3-phenylurea herbicides such as3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron),3-(4-chlorophenyl)-1-methoxy-1-methylurea (monolinuron),3-(4-bromo-4-chlorophenyl)-1-methoxy-1-methylurea (chlorobromuron).

L. thiolcarbamate herbicides such as S-propyl dipropylthiocarbamate(vernolate);

M. 1,2,4-triazin-5-one herbicides such as4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazine-5-one (metamitron)and 4-amino-6-t-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one(metribuzin);

N. benzoic acid herbicides such as 2,3,6-trichlorobenzoic acid(2,3,6-TBA), 3,6-dichloro-2-methoxybenzoic acid (dicamba) and3-amino-2,5-dichlorobenzoic acid (chloramben);

O. anilide herbicides such asN-butoxymethyl-chloro-2′,6′-diethylacetanilide (butachlor), thecorresponding N-methoxy compound (alachlor), the correspondingN-i-propyl compound (propachlor), 3′,4′-dichloropropionanilide(propanil) and 2-chloro-N-[pyrazol-1-ylmethyl]acet-2′-6′-xylidide(metazachlor);

P. dihalobenzonitrile herbicides such as 2,6-dichlorobenzonitrile(dichlobenil), 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) and3,5-diiodo-4-hydroxybenzonitrile (ioxynil);

Q. haloalkanoic herbicides such as 2,2-dichloropropionic acid (dalapon),trichloroacetic acid (TCA) and salts thereof;

R. diphenylether herbicides such as 4-nitrophenyl2-nitro-4-trifluoromethylphenyl ether (fluorodifen), methyl5-(2,4-dichlorophenoxy)-2-nitrobenzoate (bifenox),2-nitro-5-(2-chloro-4-trifluoromethylphenoxy)benzoic acid (acifluorfen)and salts and esters thereof, 2-chloro-4-trifluoromethylphenyl3-ethoxy-4-nitrophenyl ether (oxyfluorfen) and5-(2-chloro-4-(trifluoromethyl)phenoxy)-N-(methylsulfonyl)-2-nitrobenzamide(fomesafen); and

S. phenoxyphenoxypropionate herbicides such as2-(4-(4′-trifluoromethylphenoxy)-phenoxy)-propionic acid methylester(trifop-methyl),2-(4-((5-trifluoromethyl)-2-(pyridinyl)oxy)phenoxypropanoic acid(fluazifop) and esters thereof,2-(4-((3-chloro-5-trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoicacid (haloxyfop) and esters thereof,2-(4-((6-chloro-2-quinoxalinyl)oxy)phenoxypropanoic acid (xylofop) andesters thereof; and

T. cyclohexanedione herbicides such as2,2-dimethyl-4,6-dioxo-5-(1-((2-propenyloxy)amino)-butylidine)cyclohexanecarboxylic acid (alloxydim) and salts thereof,2-(1-ethoxyimino)butyl-5-(2-(ethylthio)propyl)-3-hydroxy-2-cyclohexen-1-one(sethoxydim),2-(1-(3-chloroallyloxyimino)butyl)-5-(2-ethylthiopropyl)-3-hydroxycyclohex-2-enone (cloproxydim),2-(1-ethoxyimino)butyl)-3-hydroxy-5-thian-3-yl cyclohex-2-enone(cycloxydim); and

U. sulfonyl urea herbicides such as2-chloro-N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-aminocarbonyl)benzenesulphonamide(chlorosulfuron), methyl2-((((4,6-dimethyl-2-pyrimidinyl)amino)carbonyl)amino)sulphonylbenzoicacid (sulfometuron),2-(((3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)carbonyl)amino)sulphonyl)benzoicacid (metsulfuron) and esters thereof;

V. imidazolidinone herbicides such as2-(4,5-dihydro-4-isopropyl-4-methyl-5-oxoimidazol-2-yl)quinoline-3-carboxylicacid (imazaquin), methyl6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate and p-toluateisomer (AC 222293)

W. arylanilide herbicides such as1-methylethyl-N-benzoyl-N-(3-chloro-4-fluorophenyl)-L-alanine(flamprop-isopropyl), ethylN-benzoyl-N-(3,4-dichlorophenyl)-DL-alaninate (benzoylprop-ethyl),N-(2,4-difluorophenyl)-2-(3-(trifluoromethyl)phenoxy)-3-pyridinecarboxamide(diflufenican); and

X. amino acid herbicides such as N-(phosphonomethyl)glycine (glyphosate)and DL-homoalanin-4-yl(methyl)phosphinic acid (phosphinothricin) andtheir salts and esters; and

Y. organoarsenical herbicides such as monosodium methanearsonate (MSMA);and

Z. miscellaneous herbicides including N,N-dimethyldiphenylacetamide(diphenamid), N-(1-naphthyl)phthalamic acid (naptalam) and3-amino-1,2,4-triazole, 2-ethoxy-2,3-dihydro-3,3-dimethylbenzofuranmethanesulfonate (ethofumesate), 7-oxabicyclo(2.2.1)heptane.1-Methyl-4-(1-methylethyl)-2-(2-methylphenylmethoxy)-exo (cinmethylin);

AA. Examples of useful contact herbicides include:

bipyridylium herbicides such as those in which the active entity is the1,1′-dimethyl-4,4′-dipyridylium ion (paraquat) and those in which theactive entity is the 1,1′-ethylene-2,2′-dipyridylium ion (diquat);

The following Examples illustrate the preparation of representativecompounds of the invention.

EXAMPLE 1

This Example illustrates the preparation of Compound No. 1 in Table I.

To 2-thiophenecarboxylic acid chloride (1.2 ml) in dry dichloromethane(50 ml) was added Dimedone (1.57 g) and triethylamine (1.7 ml) dropwise.The reaction mixture was stirred at room temperature for 1½ hours andthen evaporated to dryness to yield a soft solid (4.83 g).

Dry acetonitrile (35 ml) was added to the solid which dissolved to forma yellow solution. Triethylamine (3.2 ml) and acetone cyanohydrin (6drops) were added to the solution which was then stirred at roomtemperature for 2 hours. On purification by column chromatography usinga silica column with an eluent consisting of hexane 50:ethyl acetate50:acetic acid 1, the main orange band was collected and crystallised onstanding to Compound No. 1 (97% yield).

EXAMPLE 2

This Example illustrates the preparation of Compound No. 2 in Table I.

A mixture of 2,5-dichlorothiophene acid chloride (1.06 g) and Dimedone(0.70 g) in dry acetonitrile (25 ml) was cooled in a water bath andtriethylamine (0.76 ml) and acetonitrile (5 ml) added dropwise. Themixture was stirred at room temperature for ½ hour, triethylamine (1.4ml) and acetonecyanohydrin (4 drops) added and stirring was continuedfor 20 hours, after which the solution was evaporated to dryness.

The residue was dissolved in ethyl acetate and the solution applied to asilica column using a eluent of hexane 50:ethylacetate 50:acetic acid 1and the main orange band collected and solidified.

Further purification by recrystallisation from hexane and columnchromatography as described above yielded Compound No. 2 (0.24 g).

EXAMPLE 3

This Example illustrates the preparation of Compound No. 5 in Table I.

5-Bromo-2-thiophenecarboxylic acid (2.09 g), dry dichloroethane (30 ml)and thionyl chloride (0.75 ml) were heated together at 80° C. for 4hours. The mixture was cooled in an ice water bath and Dimedone (1.40 g)added followed by the dropwise addition of triethylamine (2.8 ml) in drydichloroethane (5 ml). After 1 hour at room temperature furthertriethylamine (2.8 ml) and acetonecyanohydrin (6 drops) were added andstirring continued for 15 hours. The solution was then left for a totalof 3 days at room temperature, after which time it was evaporated todryness, the residue dissolved in ethylacetate and the resultingsuspension applied to a silica column and eluted with hexane50:ethylacetate 50:acetic acid 1 and the main orange band collectedwhich solidified to give Compound No. 5 as an orange solid (1.26 g).

EXAMPLE 4

This Example illustrates the preparation of Compound No. 6 in Table I.

5-Methyl-2-thiophenecarboxylic acid (0.71 g), cyclohexan-1,3-dione (0.5g) and a small amount of (4-dimethylaminopyridine) (100 mgs) weredissolved in dry dichloromethane (20 ml) at 15° C. anddicyclohexylcarbodiimide (1.02 g) added. The reaction mixture wasstirred at 18-20° C. for 3-4 hours and then filtered and evaporated. Tothe resulting oil were added dry acetonitrile (8 ml), acetonecyanohydrin (4 drops) and triethylamine (1.4 ml) and the mixture stirredfor 2-3 hours at room temperature and subsequently evaporated todryness.

The residue was purified by column chromatography using as eluent,hexane 70:ethylacetate 30:acetic acid 3 and the main yellow bandcollected and evaporated to give Compound No. 6 as a cream solid (0.38g).

EXAMPLE 5

This Example illustrates the preparation of compound 10 in Table 1.

5-Chloro-2-thienoyl chloride (8.0 g, 44 mmol) and 1.3-cyclohexanedione(5.0 g, 44 mmol) were dissolved in 150 ml of methylene chloride.Triethylamine (15 ml, 110 mmol) was added and the resulting mixture wasstirred at room temperature for fifteen minutes. The solution was washedwith dilute hydrochloric acid, 5% potassium carbonate and saturatedsodium chloride, dried over anhydrous magnesium sulfate and concentratedin vacuum. The residue was dissolved in 100 ml of acetonitrile.Triethylamine (15 ml, 110 mmol) and acetone cyanohydrin (0.2 g) wereadded and the mixture stirred at room temperature for 2 hours. Afterdilution with ether, the solution was washed with dilute hydrochloricacid and extracted with 5% potassium carbonate. The basic extract wasacidified with hydrochloric acid and extracted with ether. The etherextract was washed with saturated sodium chloride, dried over magnesiumsulfate and concentrated in vacuum yielding 3.8 g of the desired product(mp. 31-35° C.). It was identified as such by nuclear magnetic resonancespectroscopy, infrared spectroscopy and mass spectroscopy.

EXAMPLE 6

This Example illustrates the preparation of compound 42 in Table 1.

4-Carboxy-1-methyl-5-trifluoromethyl-1H-pyrazole (5.0 g, 26 mmol) wasdissolved in a mixture of tetrahydrofuran (25 ml) and acetonitrile (25ml). Dicyclohexylcarbodiimide (5.3 g, 26 mmol) was added and theresulting mixture was stirred at room temperature for 5 minutes.1,3-Cyclohexanedione (2.9 g, 26 mmol) dissolved in a mixture oftetrahydrofuran (25 ml) and acetonitrile (25 ml) was added and themixture stirred at room temperature overnight. The reaction mixture wasfiltered and the filtrate was concentrated in vacuum. The residue wasdissolved in acetonitrile (100 ml). Triethylamine (9 ml, 66 mmol) andtrimethylsilyl cyanide (0.2 g) were added and the mixture stirred at 50°C. for 4 hours. After dilution with ether, the solution was washed withdilute hydrochloric acid and extracted with 5% potassium carbonate. Thebasic extract was acidified with hydrochloric acid and extracted withether. The ether extract was washed with saturated sodium chloride,dried over anhydrous magnesium sulfate and concentrated in vacuumyielding 2.7 g of the desired product as a yellow solid (mp. 118-122°C.). It was identified as such by nuclear magnetic resonancespectroscopy, infrared spectroscopy and mass spectroscopy.

Compounds 7-71 and 78 were prepared by methods analogous to thoseemployed in Examples 5 or 6.

EXAMPLE 7

This Example illustrates the preparation of compound 79 in Table II.

The ester (i) (4.17 g was dissolved in isopropylalcohol (50 ml) andsodium hydroxide (0.77 g) in water (5 ml) added with stirring. Themixture was heated under reflux for 2 hours, and then poured into 2Maqueous hydrochloric acid to quench the reaction. The product was thenextracted into ethyl acetate and the extracts dried over magnesiumsulphate. Concentration under reduced pressure gave the acid (ii) as ayellow solid.

Step b

2,2,4,4-Tetramethyl-cyclohexan-1,3,5-trione (0.50 g) and the acid fromstep (a)) (0.58 g) were stirred together in dry dichloromethane DMAP (ca50 mg) and dicyclohexyl carbodiimide (0.47 g) were added and the mixturewas allowed to stand to room temperature overnight. The reaction mixturewas filtered and concentrated under reduced pressure to give a yellowsolid. This solid was dissolved in acetonitrile and triethylamine (0.76ml) added. Acetone cyanohydrin (4 drops) were added and the mixturestirred at room temperature for 5 hours. It was then poured into 2Maqueous hydrochloric acid, extracted with ethyl acetate, dried andconcentrated under reduced pressure and recrystallised fromethanol/ethyl acetate to give compound 78 as a yellow crystalline solid(0.15 g).

EXAMPLE 8

This Example illustrates the preparation of compound 80 in Table 2.

Step a

Ethyl 2,4-dimethylthiazole-5-carboxylate (3.0 g, 0.016 mol) wasdissolved in isopropyl alcohol (50 ml) and sodium hydroxide (0.71 g,0.018 mol) in H₂O (5 ml) added. The reaction mixture was stirred at roomtemperature for 1 hour then heated under reflux for 1 hour, poured intoH₂O, acidified with 2M hydrochloric acid solution extracted with ethylacetate. The aqueous phase was concentrated under reduced pressure,triturated with water, and filtered to give a pale pink solid (mpt. 200°C.).

Step b

2,2,4,4-Tetramethylcyclohexan-1,3,5-trione (0.50 g, 2.75 mmol) wasdissolved in dichloromethane (30 ml) and the product from step (a), andDMAP (ca 50 mg) and dicyclohexylcarbodiimide (0.47 g) added. Thereaction mixture was stirred at room temperature for 1 hour, and thenfiltered and concentrated under reduced pressure. The residue wasdissolved in acetonitrile (30 ml) and triethylamine (0.76 ml) was added,together with acetone cyanohydrin (4 drops). The reaction mixture wasstirred at room temperature for 2 hours and then heated under reflux for1½ hours. Reaction mixture was then poured into 2M aqueous hydrochloricacid solution, extracted with ethyl acetate, dried and concentratedunder reduced pressure to give a yellow oil and solid which wastriturated repeatedly with CH₂Cl₂ to remove triketone starting material.Compound 80 was obtained as a yellow oil.

Compounds 72 and 83 were prepared by methods analogous to thosedescribed in Examples 7 and 8.

EXAMPLE 9

This Example illustrates the preparation of compound 80 in Table II.

Step a

5-(2-Pyridyl)thiophene-2-carboxylic acid (1.0 g) was stirred in toluene(50 ml) and dimethylformamide (3 drops). Thionyl chloride (1.6 ml, 9.76mmol) was added and the reaction mixture stirred at room temperature for6 hours, then heated under reflux for 1 hour and filtered. Concentrationunder reduced pressure gave a yellow solid (1.08 g).

Step b

Compound (iii) (0.50 g) and the acid chloride from step (a) (0.63 g),were stirred in dry acetonitrile (15 ml) at room temperature.Triethylamine (0.38 ml) was added, the cloudy yellow suspension changingto clear orange then to clear dark yellow as the triethylamine wasadded. The reaction mixture was then stirred at room temperature for 2hours and triethylamine (0.76 ml) and acetone cyanohydrin (4 drops) wereadded. After stirring at room temperature for 6 hours the reactionmixture was poured into H₂O (50 ml), acidified with 2M HCl (100 ml),extracted with EtOAc (100 ml), the EtOAc phase was washed with 50%NA₂CO₃ solution (100 ml) and the base layer then acidified with 2M HCl.The mixture was then extracted with CH₂Cl₂, and the CH₂Cl₂ phase washedwith brine (25 ml), dried over MgSO₄, filtered and concentrated underreduced pressure to give a bright yellow solid.

Compound 81 was obtained by prep plate chromatography using the solventsystem ethylacetate/hexane/acetic acid in the ratio 75:175:1. It wasobtained as a yellow oil that crystallised on standing.

Compounds 73, 74, 75 and 76 were prepared by methods analogous to thosedescribed in Example 9.

EXAMPLE 10

This Example illustrates the preparation of compound 77.

The salt (v) (0.84 g) was treated with toluene (35 ml) and DMF (5 drops)added. The stirred suspension was treated dropwise with oxalyl chloride(0.75 ml). This caused a colour change to purple and considerableeffervescence. The mixture was stirred overnight at room temperature andthen evaporated under reduced pressure to give an off white solid. Thiswas treated with acetonitrile (15 ml) and partially dissolved. Themixture was stirred with ice-bath cooling and cyclohexane-1,3-dione (0.6g) was added. Triethylamine (0.75 ml) was then added dropwise. Most ofthe precipitate dissolved. The mixture was stirred with continuedcooling for 3 hours. Allowed to obtain room temperature and then treatedwith acetone cyanohydrin (6 drops). Triethylamine (1.8 ml) was thenslowly added.

The mixture was then stirred at room temperature for 4 hours then leftto stand over the weekend. A yellow and orange solution resulted. Thiswas filtered and the filtrate poured into water (100 mls). The resultingalkaline solution was acidified with dilute HCl and became cloudy.

The mixture was extracted with dichloromethane to give a yellow organiclayer. This was extracted with sodium carbonate solution and the aqueouslayer acidified with dilute hydrochloric acid. The cloudy mixture formedwas extracted with dichloromethane and the organic phase washed withwater dried over magnesium sulphate and then filtered and evaporated togive a yellow oil which set on standing to give compound 77 as a yellowsolid (0.5 g).

Biological Data

As previously mentioned, the herein described compounds produced in theabove-described manner are phytotoxic compounds which are useful andvaluable in controlling various plant species. Selected compounds ofthis invention were tested as herbicides in the following manner.

Pre-emergence herbicide test. On the day preceding treatment, seeds ofseven different weed species are planted in loamy sand soil inindividual rows using one species per row across the width of a flat.The seeds used are green foxtail (FT) (Setaria viridis), watergrass (WG)(Echinochloa crusgalli), wild oat (WO) (Avena fatua), annualmorningglory (AMG) (Ipomoea lacunosa), velvetleaf (VL) (Abutilontheophrasti), Indian mustard (MD) Brassica juncea), and yellow nutsedge(YNG) (Cyperus esculentus). Ample seeds are planted to give about 20 to40 seedlings per row, after emergence, depending upon the size of theplants.

Using an analytical balance, 600 milligrams (mg) of the compound to betested are weighed out on a piece of glassine weighing paper. The paperand compound are placed in a 60 millileter (ml) wide-mouth clear bottleand dissolved in 45 ml of acetone or substituted solvent. Eighteen ml ofthis solution are transferred to a 60 ml wide-mouth clear bottle anddiluted with 22 ml of a water and acetone mixture (19:1) containingenough polyoxyethylene sorbitan monolaurate emulsifier to give a finalsolution of 0.5% (v/v). The solution is then sprayed on a seed flat on alinear spray table calibrated to deliver 80 gallons per acre (748 L/ha).The application rate is 4 lb/acre (4.48 Kg/ha).

After treatment, the flats are placed in the greenhouse at a temperatureof 70 to 80° F. and watered by sprinkling. Two weeks after treatment,the degree of injury or control is determined by comparison withuntreated check plants of the same age. The injury rating from 0 to 100%is recorded for each species as percent control with 0% representing noinjury and 100% representing complete control.

Post Emergence Test

Post emergence results were obtained using similar methods except thatthe compounds were applied to the young plants.

The results of the tests are shown in the following Tables III and IV.

TABLE III Pre-emergence Herbicidal Activity Compound Application Rate4.00 lb/ac No. FT WG WO AMG VL MD YNG 4 0 0 0 0 100 10 35 6 25 20 0 0 00 0 7 8 0 5 0 10 70 70 11 20 0 0 0 25 60 0 12 20 25 0 0 0 25 0 14 0 0 05 0 20 0 16 0 0 0 0 85 25 70 18 50 35 0 0 100 10 0 19 60 0 0 0 20 100 2520 30 25 0 25 100 95 30 21 0 0 0 0 100 100 30 22 0 — 25 0 0 0 0 23 25 4020 0 0 0 0 29 70 100 95 30 95 100 80 30 100 100 80 85 100 100 80 31 0 100 0 10 40 80 32 0 0 0 0 0 0 80 33 0 0 0 0 0 0 30 35 0 30 0 0 30 0 30 360 0 30 80 90 10 0 37 30 0 0 0 0 0 0 38 0 0 0 0 5 0 0 40 80 50 30 10 5050 70 41 90 100 20 30 100 95 80 42 100 50 100 100 100 95 80 43 90 30 90100 100 60 80 44 90 85 20 100 100 5 80 45 100 100 20 100 100 90 80 46 2085 20 100 100 60 80 47 30 80 0 100 100 80 80 48 80 80 0 100 100 20 70 49100 20 100 100 100 90 80 50 60 90 0 100 100 95 80 51 100 90 30 100 10040 30 52 100 95 60 100 90 75 70 53 80 70 20 100 100 10 0 54 100 80 20100 60 100 0 55 100 70 30 98 90 85 20 56 95 70 20 80 95 75 60 57 100 9020 95 95 75 80 60 20 25 0 0 0 0 0 65 30 0 0 0 0 0 0 66 0 — 25 0 0 0 0 6925 40 20 0 0 0 0 78 100 100 90 100 90 90 80

Compounds 13, 15, 24, 25, 26, 27, 28, 34, 39 showed no pre-emergenceactivity against the test species at the given rate of application.

TABLE IV Pre-emergence Herbicidal Activity Compound Application Rate4.00 lb/ac No. FT WG WO AMG VL MD YNG 4 40 25 0 85 100 100 40 6 20 30 025 70 50 0 7 0 30 0 10 0 10 0 9 40 30 10 0 100 95 0 10 0 30 0 0 0 40 011 20 30 0 35 20 30 0 12 0 0 0 0 25 25 0 13 10 20 0 0 15 25 0 14 0 0 015 0 20 0 15 0 0 0 20 20 80 0 16 0 0 0 0 60 100 80 18 0 20 10 100 100 9035 19 0 0 0 25 60 100 70 20 20 0 0 25 100 100 0 21 0 25 0 40 70 80 0 220 20 0 0 0 35 0 24 20 0 — 30 20 40 0 25 20 25 0 0 35 50 15 26 0 0 0 0 00 20 28 0 40 0 20 40 80 0 29 65 80 80 10 90 80 50 30 80 80 40 30 30 5080 31 0 50 0 5 80 80 60 32 0 0 0 0 50 50 30 33 0 0 0 5 30 0 10 35 0 30 00 10 10 0 36 10 10 80 100 100 100 70 40 80 50 30 10 50 50 70 41 60 90 8020 100 80 70 42 100 90 80 100 100 90 80 43 90 85 50 100 100 100 70 44 1020 10 10 90 80 30 45 85 90 90 100 90 90 75 46 20 40 10 90 80 20 70 47 1040 0 80 80 60 70 48 5 40 0 100 95 30 60 49 30 70 5 60 60 20 80 50 20 605 60 60 40 80 51 30 40 20 80 100 25 0 52 50 60 50 85 90 40 30 53 10 10 080 80 5 0 54 10 30 10 60 60 10 0 55 40 50 30 50 30 40 10 56 20 50 40 6080 20 30 57 50 50 50 80 80 40 40 58 40 30 10 0 100 95 0 60 20 30 0 25 7080 0 61 0 0 0 0 25 25 0 62 10 20 0 0 15 25 0 63 0 0 0 15 0 20 0 64 0 0 020 20 50 0 66 0 0 0 0 5 0 0 70 40 35 20 15 70 60 20 71 50 60 0 15 10 4010 78 85 80 80 80 85 70 80

Glasshouse Tests for Herbicidal Activity

The compounds were applied to the following species Lettuce (LT), Tomato(TO), Avena fatua (Av) and Setaria viridis (St) using a travelling boomtrack sprayer at a volume equivalent to 1000 l ha⁻¹ and atconcentrations corresponding to application rates 10 kg ha⁻¹.Assessments were made for pre-emergence activity 17-20 days after directspraying onto the seed, the seed having been covered with a compost forthat period. Assessments were also made for post-emergence activity 13days after spraying onto young plants.

The assessment scale used was as follows:

0=0-25% damage

1=26-50% damage

2=51-75% damage

3=76-100% damage

The results of this test are shown in Table V.

TABLE V PRE OR POST COMPOUND EMERGENCE DAYS AFTER TEST PLANTS 4 NO.APPLICATION TEST Lt To Av St 72 Post 13 3 3 3 3 Pre 17 3 3 0 2 73 Post13 3 3 3 3 Pre 20 3 3 3 3 76 Post 13 0 0 0 0 Pre 20 0 0 0 0 75 Post 13 21 0 0 Pre 20 3 2 0 0 79 Post 13 3 3 3 3 Pre 20 3 3 3 3 80 Post 13 3 3 33 Pre 20 3 3 3 3 82 Post 13 3 3 2 3 Pre 17 3 3 2 3 81 Post 13 0 0 0 0Pre 17 0 0 0 0 77 Post 13 3 3 1 1 Pre 17 3 3 0 0 78 Post 13 3 3 0 0 Pre20 3 3 0 0

The herbicidal activity of the others of compounds was tested asfollows:

Each compound in the appropriate concentration was incorporated into a4% emulsion of methyl cyclohexanone and a 0.4% blend of 3.6 parts Tween20 and 1 part Span 80. Tween 20 is a Trade Mark for a surface activeagent comprising a condensate of 20 molar proportions of ethylene oxidewith sorbitan laurate. Span 80 is a Trade Mark for a surface-activeagent comprising sorbitan monolaurate. Formulation was effected bydissolving the compound in the requisite amount of solvent/surfactantblend. If necessary glass beads were added, the total liquid volumeadjusted to 5 ml with water and the mixture shaken to effect completedissolution of the compound. The formulation so prepared, after removalof beads where necessary, was then diluted to final spray volume (45 ml)with water.

The spray compositions so prepared were sprayed onto young pot plants(post-emergence test) at a rate equivalent to 1000 liters per hectare.Damage to plants was assessed 13 days after spraying by comparison withuntreated plants, on a scale of 0 to 5 where 0 is 0-10% damage, 1 is 11to 25% damage, 2 is 26-50% damage, 3 is 51-80% damage, 4 is 81-95%damage and 5 is 96-100% damage.

In a test carried out to detect pre-emergence herbicidal activity, seedsof the test species were placed on the surface of plastic trays ofcompost and sprayed with the compositions at the rate of 1000 liters perhectare. The seeds were then covered with further compost. 20 days afterspraying, the seedlings in the sprayed plastic trays were compared withthe seedlings in unsprayed control trays, the damage being assessed onthe same scale of 0 to 5.

The results of the tests are given in Table VI below.

TABLE VI RATE OF PRE- OR COMPOUND APPLICATION POST-EMERGENCE TEST PLANTS(see Table VII) NO. kg/lha APPLICATION Sb Rp Ct Sy Mz Ww Rc Bd Ip Am PiCa 4 4 Pre 3 1 — 0 1 0 0 1 0 0 1 3 Post 3 3 3 2 3 2 0 3 3 4 3 4 3 4 Pre3 3 1 0 0 0 0 0 — 0 — 0 Post 2 3 2 2 3 2 1 1 1 4 1 3 5 4 Pre 4 0 1 2 1 01 2 0 1 0 3 Post 1 0 0 0 0 0 0 1 0 0 0 0 RATE OF PRE- OR COMPOUNDAPPLICATION POST-EMERGENCE TEST PLANTS (see Table VII) NO. kg/lhaAPPLICATION Ga Xa Xs Ab Co Av Dg Al St Ec Sh Ag Cn 4 4 Pre 0 3 — 5 0 0 00 1 0 0 0 3 Post 0 — 3 3 3 2 4 2 3 3 2 1 1 3 4 Pre 0 2 — 2 0 0 0 0 3 0 20 2 Post 1 — 1 2 2 0 3 1 0 2 2 2 0 5 4 Pre 1 2 — 3 2 0 0 0 0 0 0 0 0Post 0 — 0 0 0 0 0 0 0 0 0 0 0

TABLE VII Abbreviations used for Test Plants Sb - Sugar beet Rp - RapeCt - Cotton Sy - Soybean Mz - Maize Ww - Winter wheat Rc - Rice Bd -Bidens pilosa Ip - Ipomoea purpurea Am - Amaranthus retroflexus Pi -Polygonum aviculare Ca - Chenopodium album Ga - Galium aparine Xa -Xanthium spinosum Xs - Xanthium strumarium Ab - Abutilon theophrastiCo - Cassia obtusifolia Av - Avena fatua Dg - Digitaria sanguinalis Al -Alopecurus myosuroides St - Setaria viridis Ec - Echinchloa crus-galliSh - Sorghum halepense Ag - Agropyron repens Cn - Cyperus rotundus Z/PP34248R CPH/jc 23 Feb 88

What is claimed is:
 1. A compound of formula (1):

or a salt, enamine, acylate, sulphonate, carbamate or ether derivativethereof; wherein X, X¹ and X² are independently oxygen or sulphur, R¹ isan optionally substituted cycloalkyl group, and Y is

wherein R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ are independently selected fromhydrogen, C₁₋₄ alkyl, or C₁₋₄ alkanoyl or R¹⁶ and R¹⁷ or R¹⁸ and R¹⁹ orR²⁰ and R²¹ together with the carbon atom to which they are attachedform a C₃₋₆ cycloalkyl ring; q is 0 or 1; p is 0, 1 or 2, s is 0 or 1and Rb is alkyl or alkoxy, and R²³ is alkyl or alkoxy, provided thecompound is other than2-(cyclopentylcarbonyl)-5,5-dimethyl-1,3-cyclohexanedione or2-(cyclopentylcarbonyl)-1,3-cyclopentanedione.
 2. A compound accordingto claim 1 wherein R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ are hydrogen ormethyl.
 3. a herbicidal composition comprising a compound of formula (I)as defined in claim 1 in combination with a carrier or diluent.
 4. Amethod of killing or controlling unwanted plant species which methodcomprises applying to the plant or to the locus thereof a compound offormula (I)

or a salt, enamine, acylate, sulphonate, carbamate or ether derivativethereof; wherein X, X¹ and X² are independently oxygen or sulphur, R¹ isan optionally substituted cycloalkyl group, and Y is

wherein R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ are independently selected fromhydrogen, C₁₋₄ alkyl, or C₁₋₄ alkanoyl or R¹⁶ and R¹⁷ or R¹⁸ and R¹⁹ orR²⁰ and R²¹ together with the carbon atom to which they are attachedform a C₃₋₆ cycloalkyl ring; q is 0 or 1; p is 0, 1 or 2, s is 0 or 1and Rb is alkyl or alkoxy, and R²³ is alkyl or alkoxy, provided thecompound is other than2-(cyclopentylcarbonyl)-5,5-dimethyl-1,3-cyclohexanedione.